1. Field of the Invention
The invention broadly relates to skateboards.
2. Prior Art
A skateboard is comprised of an elongated board with a pair of trucks attached underneath. Each truck is comprised of a base plate attached to the board, an axle attached to the base plate with a bolt, and wheels attached to the axle. The axle has an upwardly projecting pin which is positioned inside a pin receiving hole in the base plate. The bolt is positioned through an oversized hole in a mounting portion of the axle. The bolt is centered within the hole by resilient bushings on either side of the mounting portion. The bolt and the pin form a divergent angle in the direction towards the board. When the board is rolled about a longitudinal axis to either side by foot pressure, the axle is pivoted about the pin to steer the wheels in a corresponding direction. The trucks are mounted as mirror images of each other, so that they simultaneously steer in opposite directions in response to board roll.
The resilient bushings provide compliance to enable the bolt to move laterally within the hole in the mounting portion, and provide increasing roll resistance with increasing roll angle of the board. Roll resistance is determined by the hardness of the bushings, and the clamping force applied on the bushings by the bolt, which is adjustable for tuning roll resistance. The bushings must provide enough resistance to prevent the wheels from steering too easily, that is, to provide suitable directional stability. Higher resistance provides good directional stability but limits turning radius, whereas lower resistance enables a tight turning radius but sacrifices some directional stability.